Mapping for Displacement Modifier
Start with a simple cube, add Subdivision Surface to produce enough geometry for decent displacing (you can add another one after Displace modifier for more smoothing).

Add Displace modifier, press New button, go into texture tab and select Voronoi texture.

In Displace modifier settings there are some options for texture coordinates: UV, Local, Global, Object.
There is no usual coordinates offset as in materials, so you need to bind texture to some object. Thus location, rotation and scale of this object will affect texture.

"Wire sphere" around the rock is Empty, which is controlling texture: